Avg K/D vs Total K/D of the session

So, for now when TRN calculates K/D for a gaming session or for a day, it calculates it differently than calculating it as a total for your Overview
And I was wondering what is the reasoning for this.
For example, playing two games, on one you go 10/5 and the other game goes worse resulting in 5/10.

K/D of one game is 2.0, and K/D of the other game is 0.5
In total you had 15 kills and 15 deaths, resulting in K/D 1.0
But you can also calculate it as an Average of these two K/Ds, resulting in K/D 1.25.

Both resulting in wildly different results.
And your Overview calculates your total K/D, while Last session on Homescreen calculates it as an average K/D of the K/Ds. Which is kinda confusing.